System and process for producing a metallic article

ABSTRACT

According to one or more embodiments, a hot-stamping device includes first and second die portions including an alloy of metal M, the alloy of metal M having higher heat conductivity than ferrous alloy, and a cooling circuit in communication with at least one of the first and second die portions. The metal M may be copper. The alloy of metal M may include greater than 50 percent by weight of metal M. The first and second die portions may each independently include a greater than 50 percent by weight of the alloy of metal M.

TECHNICAL FIELD

The disclosed inventive concept relates generally to system and method for producing a metallic article.

BACKGROUND

In certain existing methods, draw/form dies for hot-stamping are often expensive to build, expensive to maintain and have relatively short service lives compared to dies used in cold stamping conducted at ambient temperatures. In hot-stamping, the high temperatures of the blank which enters the die with an entry temperature of around 800 to 850 degrees Celsius promote wear related failure mechanisms including galling, thermal checking such as surface fatigue, and decarburization, all of which tend to soften the die's surface and make the die vulnerable to abrasive wear.

It would thus be advantageous if system and method for producing a metallic article may be provided to solve one or more of these identified problems.

SUMMARY

The disclosed inventive concept is believed to overcome one or more of the problems associated with producing a metallic article.

In one or more embodiments, a hot-stamping device includes first and second die portions including an alloy of metal M, the alloy of metal M having higher heat conductivity than ferrous alloys, and a cooling circuit in communication with at least one of the first and second die portions. In certain instances, the cooling circuit includes a number of cooling channels made of ferrous alloys.

The metal M may be copper. The alloy of metal M may include greater than 50 percent by weight of metal M. The first and second die portions may each independently include greater than 50 percent by weight of the alloy of metal M.

The first and second die portions may include first and second surface sections, respectively, the first and second surface sections together defining a cavity and each independently including the alloy of metal M.

The first and second die portions may include first and second body sections adjacent the first and second surface sections, respectively, the first and second body sections independently including at least 20 percent by weight of the alloy of metal M less than the first and second surface sections, respectively.

In one or more other embodiments, a method of hot-stamping includes subjecting a metallic part to a hot-stamping device as described herein.

The above advantages and other advantages and features will be readily apparent from the following detailed description of embodiments when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of embodiments of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples wherein:

FIG. 1 illustratively depicts a system for producing a metallic article according to one or more embodiments;

FIG. 2 illustratively depicts a non-limiting process for producing the metallic article referenced in FIG. 1;

FIG. 3A illustratively depicts a partial exploded view of the system referenced in FIG. 1;

FIG. 3B illustratively depicts a cross-sectional view (not to scale) of the system referenced in FIG. 3A;

FIG. 4 illustratively depicts an alternative partial exploded view of the system referenced in FIG. 1;

FIG. 5A illustratively depicts an alternative partial exploded view of the system referenced in FIG. 1; and

FIG. 5B illustratively depicts a cross-sectional view (not to scale) of the system referenced in FIG. 5A.

DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS

As referenced in the FIGS., the same reference numerals are used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.

As is described herein elsewhere, the present invention in one or more embodiments is advantageous at least in that hot-stamping dies may be built from a material that provides relatively greater heat conductivity and hence more efficient cooling for quenching the drawn/stamped part. The material may include a metal or metal alloy that is not only suitable for the hot-stamping environment but also provides one or more benefits that cannot be readily delivered by the existing ferrous alloys such as iron or steel.

In one or more embodiments, and as illustratively depicted in FIG. 1, a hot-stamping device generally shown at 100 includes a stamping press 110, first and second die portions 112, 114 located in the stamping press 110 and including an alloy of metal M, the alloy of metal M having higher heat conductivity than ferrous alloy, and a cooling circuit 116 in communication with at least one of the first and second die portions 112, 114.

For illustration purposes, only two pairs of first and second die portions 112, 114 are depicted in FIG. 1. However, the hot-stamping device 100 does not have to be limited to only two pairs of first and second die portions 112, 114. When needed, less or more than one two sets of first and second die portions 112, 114 may be employed and be employed in any suitable arrangements.

The hot-stamping device 100 may be used in connection with one or more other components which can be collectively referred as a hot-stamping system generally shown at 102 as referenced in FIG. 1.

FIG. 2 illustratively depicts a process generally shown at 200 for making a metallic article referenced in FIG. 1. In a non-limiting example, and as depicted in FIG. 1 in view of FIG. 2, a metallic source material is provided via a source stand 120 to a table cutter 108; and there the metallic source material is cut into desirable shapes to form one or more metallic parts 118. This step is also referenced as step 202 in FIG. 2.

At step 204, one or more of the metallic parts 118 may be transferred to a furnace 104 either manually or via a robot 106. The one or more metallic parts are heated to an elevated temperature within the furnace 104 at step 206.

Immediately after the heating, the one or more metallic parts 118 may be removed at step 208, optionally via another robot (not shown), to be placed within a cavity 122 defined by the cavity 122.

At step 210, the metallic part 118 is stamped by the first and second die portions 112, 114 to adopt the shape defined by the opposing surfaces of the first and second die portions 112, 114.

During the stamping and compressing, the first and second die portions 112, 114 may each be independently cooled by being in communication with the cooling circuit 116. The cooling effect may be imparted onto the first and second die portions 112, 114 via a flow of cold liquid such as cold water delivered through the cooling circuit 116. Because at least one of the first and second die portions 112, 114 include the alloy of metal M which has relatively greater heat conductivity, the cooling effect delivered by the cooling circuit 116 is enhanced by the use of the first and second die portions 112, 114 including the alloy of metal M. Consequently, the metallic part 118 may be cooled more effectively and quickly by being in contact with the first and second die portions 112, 114. A relatively quicker cooling or quenching affords the metallic part 118 as stamped with relatively greater strength and desirable metallic structure.

The metal M may be of any suitable metal, provided that the alloy of metal M has a higher heat conductivity than ferrous alloy. Without wanting to be limited to any particular theory, it is believed that the alloy of metal M has a substantial impact on thermal conductivity in comparison to its corresponding neat metal M. In addition, different metal alloys may also have measurable differences in thermal conductivity. In the case for copper, it is generally accepted that copper alloys as a group may be several times more thermal conductive than ferrous alloys.

A non-limiting list of metal M includes copper, silver and aluminum. In certain instances, the metal M is copper.

The alloy of the metal M may take any suitable form. Non-limiting examples of the alloy of the metal M include copper alloyed with one or more of beryllium, tin and zinc. Without wanting to be limited to any particular theory, it is believed that beryllium helps create strength, tin helps make bronze and zinc helps make brass.

The metal M may be greater than 50 percent by weight of the alloy of metal M. Alloy families are typically identified by the metal element which makes up the majority of the composition. By way of example, a copper based alloy would contain 50% or more elemental copper by weight. Silver alloys may be used; however, silver alloys may be too expensive relative to copper alloys. Aluminum alloys may also be used; however, aluminum alloys may not have the necessary compressive strength.

The first and second die portions 112, 114 may each independently include a greater than 50 percent by weight of the alloy of metal M. A non-limiting consideration here is that the first and second die portions 112, 114 may merely include the alloy of metal M but not entirely be made of the latter for monetary considerations. In these designs, the base of the first and second die portions 112, 114 may be a ferrous alloy such as cast iron, cast steel and/or wrought steel.

In certain instances, and as depicted in FIG. 3A, the first and second die portions 112, 114 may each include first and second surface sections 302, 304 together defining the cavity 122 therein between, the first and second surface sections 302, 304 each independently including the alloy of metal M. The first and second die portions may each include first and second body sections 308, 310 adjacent the first and second surface sections 302, 304, respectively. This may be a design wherein the first and second body sections 308, 310 may be constructed of a relatively more cost efficient material while the relatively enhanced heat conductivity is delivered by the first and second surface sections 302, 304 which contact the metallic part 118 to be inserted within the cavity 122. The thickness or weight of the first and second surface sections 302, 304 may be varied relative to the thickness or weight of the first and second body sections 308, 310 according to certain specific requirements of the stamping project at hand. For instance, the relative thickness or weight may be varied according to the size of the metallic part 118 and/or the resultant cooling requirement specific to the metallic part 118.

However, a general direction is that the first and second surface sections 302, 304 should each independently contain relatively more of the alloy of metal M than the first and second body sections 308, 310. In certain instances, the first and second body sections 308, 310 each independently include at least 20, 30, 40, 50, 60, 70, 80, or 90 percent by weight of the alloy of metal M less than the first and second surface sections 302, 304, respectively. In certain instances, the first and second body sections 308, 310 each independently include less than 10, 5 or 1 percent by weight of the alloy of metal M.

The first and second surface sections 302, 304 may be provided with a number of cooling channels 326. The cooling channels 326 may be of any suitable shape in cross-section and may be constructed of any suitable material. The cooling channels 326 may be provided as a single layer or multiple layers as needed. The cooling channels 326 may be collectively connected to an inlet 328 and an outlet 330 for the transport of a cooling fluid, which is optionally water.

The cooling channels 326 may be formed via machine drilling so as to create openings in the form of channels. Drilling itself can be both costly and labor intensive. An alternative may be to form the channels via casting, wherein a liquid melt of a metallic casting material is introduced into a cast preformed with cores, the voids left behind later become the cooling channels.

Cores may generally be made from sand held together with a binding agent. After the liquid metal solidifies the binding agent breaks down and the crumbling sand may then be removed from the holes, typically by shaking or sand blasting.

In these designs using sand cores, the length to diameter ratio for making holes is typically about 5 to 1. This means that cooling channels produced by cores may be too short and fat for effective heat transfer. To create cast-in cooling passages that can be used for effective heat transfer, a non-limiting way would be to place ferrous alloy tubing in the mold and pour the copper alloy around it.

In this casting process, using a copper-alloy containing liquid melt in comparison to an all ferrous liquid melt provides a synergistic benefit both in cost and performance. As all ferrous metallic material would have the relatively high melting point, a ferrous core would be very sensitive to the extreme heat required and formed during an all ferrous liquid melt casting process and may melt unfavorably. In this scenario, cooling channels may be formed in an all ferrous die via the very labor intensive drilling process and the casting may not be a viable option.

With the present invention in one or more embodiments, copper-alloy has a substantially lowered melting point in comparison to ferrous alloy; and as a result, ferrous cores may be used in a cast with copper-alloy containing liquid melt in a temperature that does not induce melting the cores. Accordingly, cooling channels may be readily and relatively easily formed via casting for the copper-alloy containing dies. In this way, not only the copper-alloy containing dies provide relatively better cooling, but also the cooling can be effected more economically as the cooling channels can be formed more cost effectively. Simply put, the present invention in one or more embodiments provides faster and cheaper cooling all at the same time.

Ferrous alloy such as steel has one of the highest melting points of all the commonly used metal alloys. Any metal gets very soft and weak when it approaches it's melting point. Therefore metal inserts in a mold can be melted or severely softened when liquid steel enters the cavity. Steel melting point is at or around 2800° F. while copper alloy melting point is at or around 1750° F. If liquid copper is poured around ferrous alloy tubing such as steel tubing, the steel tubing will stay solid and in position. Pouring liquid steel around steel tubing puts the tubes dangerously close to the melting point and they collapse and/or distort as mentioned previously. The copper alloy for the tool empowers the ability to cast-in cooling passages. To make a cast steel die ideally tubing inserted into the mold should be made out of something with a much higher melting point than steel, however there are very few metals with melting points higher than steel; mostly rare metals with no engineering significance.

Referring back to FIG. 4, and in an alternative view, reference numerals 402, 404 collectively refer to a first surface section of the first die portion 112 and a second surface section of the second die portion 114, respectively. Reference numerals 408, 410 collectively refer to a first body section of the first die portion 112 and a second body section of the second die portion 114, respectively. Reference numerals 430, 432, 434 refer to relevant portion of the first body section 408 corresponding to the binder 420, the binder 422, and the punch 424, respectively. Reference numerals 440, 442, 444 refer to relevant portion of the first surface section 402 corresponding to the binder 420, the binder 422, and the punch 424, respectively.

FIG. 4 illustratively depicts a partial cross-section of a variation to the system referenced in FIG. 3A. As illustratively depicted in FIG. 4, the first die portion 112 may include binders (a.k.a. blank-holders) 420, 422 and a punch 424 spaced apart from both the binders 420, 422. This is particular to a draw/die operation where the binders 420, 422, by coming closer to the second die part 114, provide a reasonably good positioning of the metallic part 118 as located within the cavity 122. Once the metallic part 118 is positioned within the cavity 122 and flexibly secured by the binders 420, 422 and the second die portion 114, the punch 424 may then come into contact with the metallic part 118 to impart the drawing. The term “flexibly secured” refers to the operation that is particular to the draw/die operation, in which the metallic part 118 is still movable through the area defined between each of the binders 420, 422 and the second die portion 114, as may be needed to feed the metallic material into the area defined between the punch 424 and the second die portion 114.

FIG. 3A and FIG. 4 both illustratively depict that the first and second die portions 112, 114 include surface sections and body sections. In the alternative (not shown), the first and second die portions may be constructed entirely of the material forming the surface sections. Because the material forming the surface sections tend to be relatively more costly, the practicality of the first and second die portions 112, 114 made entirely out of the material forming the surface sections may be limited by cost consideration. However, as mentioned herein elsewhere, the increased cost in building such die portions may be mitigated by a reduction in cost for forming the cooling channels. Therefore, such design is believed to still be useful relative some existing designs where die portions are constructed entirely of ferrous alloys.

FIG. 5A illustratively depicts a variation of the cross-section referenced in FIG. 3A or FIG. 4, with FIG. 5B showing a cross-section taken along lines 5B-5B. A notable difference in FIG. 5A with comparison to FIG. 3A or FIG. 4 lies in the shape and construction of cooling channels 526, which are configured in “wafer” style. Cooling liquid may be provided via a bottom surface of the second die part 114 and flows through each of the cooling channels and returns back out via an outlet (not shown).

In one or more embodiments, the disclosed invention as set forth herein overcomes the challenges faced by known production of metallic articles. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims. 

What is claimed is:
 1. A hot-stamping device comprising: first and second die portions including an alloy of metal M, the alloy of metal M having higher heat conductivity than ferrous alloy; and a cooling circuit in communication with at least one of the first and second die portions.
 2. The hot-stamping device of claim 1, wherein the metal M is copper.
 3. The hot-stamping device of claim 1, wherein the alloy of metal M includes greater than 50 percent by weight of metal M.
 4. The hot-stamping device of claim 1, wherein the first and second die portions each independently include a greater than 50 percent by weight of the alloy of metal M.
 5. The hot-stamping device of claim 1, wherein the first and second die portions include first and second surface sections, respectively, the first and second surface sections together defining a cavity and each independently including the alloy of metal M.
 6. The hot-stamping device of claim 5, wherein the first and second die portions include first and second body sections adjacent the first and second surface sections, respectively, the first and second body sections independently including at least 20 percent by weight of the alloy of metal M less than the first and second surface sections, respectively.
 7. The hot-stamping device of claim 1, wherein the cooling circuit includes a number of cooling channels contacting at least one of the first and second die portions.
 8. The hot-stamping device of claim 5, wherein the cooling circuit includes a number of cooling channels contacting at least one of the first and second surface sections.
 9. The hot-stamping device of claim 8, wherein the number of cooling channels includes ferrous alloy.
 10. The hot-stamping device of claim 1, wherein the alloy of metal M includes at least one of beryllium, tin and zinc.
 11. A hot-stamping device comprising: first and second die portions each including a copper alloy, the copper alloy including greater than 50 percent by weight of copper; and a cooling circuit in communication with at least one of the first and second die portions.
 12. The hot-stamping device of claim 11, the first and second die portions each independently include greater than 50 percent by weight of the copper alloy.
 13. The hot-stamping device of claim 11, wherein the first and second die portions include first and second surface sections, respectively, the first and second surface sections together defining a cavity and each independently including the copper alloy.
 14. The hot-stamping device of claim 13, wherein the first and second die portions include first and second body sections adjacent the first and second surface sections, respectively, the first and second body sections independently including at least 20 percent by weight of the copper alloy less than the first and second surface sections, respectively.
 15. The hot-stamping device of claim 11, wherein the cooling circuit includes a number of cooling channels including ferrous alloy and contacting at least one of the first and second die portions.
 16. The hot-stamping device of claim 14, wherein the cooling circuit includes a number of cooling channels including ferrous alloy and contacting at least one of the first and second surface sections.
 17. A method of hot-stamping, comprising: subjecting a metallic part to a cavity defined by first and second die portions, at least one of the first and second die portions including an alloy of metal M, the alloy of metal M having a higher heat conductivity than ferrous alloy.
 18. The method of claim 17, further comprising contacting at least one of the first and second die portions including the alloy of metal M with a number of cooling channels.
 19. The method of claim 18, further comprising forming the number of cooling channels via casting.
 20. The method of claim 17, further comprising contacting the metallic part with both of the first and second die portions to effect compression. 